The use of photo-curable dental composite resins is now standard in contemporary dental practice. Such dental composites consist of a mixture of liquid acrylic monomers, particulate fillers such as glass or ceramic particles, and a photo-initiator such as camphorquinone (CQ) that forms a workable composition. This composition can be cured into a hardened filling by activating the photo-initiator via an external light source, which raises it from the ground state to an excited, activated state. After combining with an amine co-initiator, an aminoalkyl free radical is formed which initiates polymerization. The mechanical properties of the cured composite resins were shown to be dependent on the curing process. It is thus highly desirable to monitor the curing status of the resin in real time as to achieve the optimum performance. However, conventional cure monitoring methods such as Raman or FTIR spectroscopy either are too slow or require sample preparation. Fluorescence spectroscopy was proposed before for real time cure monitoring. However, it generally requires a fluorescence probe to be added into the resin. In additional, all these methods require an additional light source for measuring the optical spectrum of the dental resin, which limits their practical application.
There thus exists a need for an improved method for monitoring the curing status of a dental resin. This method should require no sample preparation and be fast enough for real time cure monitoring.